Foundation tube for use as a foundation for masts, posts, pillars, etc.

ABSTRACT

A foundation for masts, posts, pillars, etc., wherein the foundation has a foundation tube (3) which is lowered into a pre-drilled hole (2) in the ground (1), where the pre-drilled hole has a diameter larger than the diameter of the tube (3) and where at least the space between tube (3) and ground (1) is filled with a casting mixture (8), e.g. concrete, a tube (3) is used which is designed with perforations (4) in its lower area. The foundation tube (3) is equipped with a coating which gives the tube protection against corrosion, and possibly also an electrical insulation. The coatings can have a rough surface in order to create the best possible adhesion to the casting mixture. In order to ensure that the coated foundation tube (3) is safely lowered into the hole, it is first lined with a casing (13), which is removed during or immediately after the casting.

The invention concerns a foundation tube for use as a foundation formasts posts, pillars, etc., wherein perforations or holes are providedin the tube for forcing casting mixture out into the space between thetube and the surrounding substance. The invention also concerns a methodfor formation of a foundation for masts, posts, etc. comprising at leastone foundation tube which is lowered into a pre-drilled hole in theground, the hole having a diameter greater than the diameter of the tubeand where at least the space between the tube and the ground is filledwith a casting mixture, e.g. concrete.

A number of different methods are known for manufacturing mastfoundations by driving tubes down into the ground, wherein the tubes arefilled with concrete and cast in position to form the finishedfoundation. It is also known in the prior art for such tubes to beequipped with perforations in order to force the concrete out throughthe tube and into the ground surrounding the tube. In this connection itis also a known procedure to first drill a hole in the ground and thenplace a perforated tube in the hole, whereupon the tube is cast inposition, as the casting mixture is forced out through the perforations,filling the space between the hole and the ground as well as the actualtube. The upper part of the tube is equipped with fastening devices fora pillar, mast or other equipment which has to be secured to thefoundation. A plurality of such tubes can also be used jointly for alarger foundation and connected to one another by means of a top plate.

This method of laying a foundation has proved to be very practical, butnevertheless there has been a need for a further improvement of themethod.

One of the problems which are encountered in laying a foundation is thatin many places there is an extremely corrosive environment at thefoundation location, both above the ground and in the ground itself, andthis can affect the tube foundation, giving it a very short workinglife.

Another problem is that in the case of masts, posts, etc. which supportlive wires or cables, a flashover can easily occur in the foundation,which is considered to be a disadvantage, particularly if this occurs atground level.

Thus it is an object of the present invention to provide a foundationtube wherein the problems of corrosion are avoided and wherein thefoundation tube is designed in such a manner that it can be securelyattached to the ground. A further object of the invention is to providean improved method of laying a foundation, whereby the problemsdescribed in the introduction can be remedied to the greatest possibleextent, thus enabling an efficient and satisfactory method to beachieved of laying a foundation for masts, posts, etc.

It is also an object of the invention to avoid the formation ofelectrical bridges between the foundations and post and ground level.

These objects are achieved with a foundation tube of the type mentionedin the introduction, which is characterized by those features indicatedin the patent claims. The invention also concerns a method for theformation of a foundation, and the method is characterized by thefeatures indicated in the patent claims.

By providing the foundation tube with an external and internal coating,especially of thermoplastic, the foundation tube is very well protectedagainst corrosive influences. By equipping the coating with a roughsurface, a particularly secure attachment is ensured during casting.Thus the foundation tube according to the invention will have a longworking life even in an extremely corrosive environment.

When laying a foundation for current-carrying pylons, a corrosioncoating also provides an insulating effect. This insulation may beachieved with an extra coating on a clean corrosion coating. On thebottom part of the foundation tube it is advantageous to also provide acoating with a rough surface in order to give the best possible adhesionto the casting mixture. The outermost coating, either the corrosioncoating or possibly the insulating coating, can also have a roughsurface in order to achieve a similar effect. Suitable coatingsproviding a rough surface or coating additives may include quartz sand.

The use of thermoplastics is preferred as a coating material, and aparticularly advantageous thermoplastic is EVO(ethylenevinylalcoholcopolymer).

According to the invention, a casing is used in the method for laying afoundation. This is very important when a foundation tube which iscoated on the outside has to be lowered into the pre-drilled hole. In anormal pre-drilled hole there would be a great risk of the coating beingdamaged during the lowering operation. A further advantage of using acasing is that a collapse of loose material is avoided, thus givingsatisfactory control of the pre-drilled hole and its subsequent fillingwith casting mixture.

The invention will now be explained in more detail by means of anembodiment which is illustrated in the drawing, in which:

FIG. 1 is a schematic view of a pre-drilled hole with casing inserted.

FIG. 2 is a schematic view of a foundation tube which has been loweredinto the pre-drilled hole with casing, casting mixture or groutingmaterial having been supplied before filling the hole,

FIG. 3 is a completed foundation manufactured in accordance with themethod according to the invention, and

FIG. 4 is a section of a foundation tube according to the invention.

The drawing illustrates only the principle of the invention, anddimensions of holes and the various tubes are not on the correct scaleand are not intended to illustrate the concept of the invention.

In the method according to the invention a foundation will bemanufactured by lowering a foundation tube 3 into the ground 1. A hole 2is drilled in the ground beforehand, which can have a larger diameterthan the diameter of the foundation tube. As illustrated in FIG. 1, acasing 13 is first lowered into the pre-drilled hole. This casing 13should have a diameter which is relatively close to the diameter of thehole, and still be easy to insert. The casing can be of any materialwhatever, e.g. a plastic tube, since the tube is intended to be pulledup during the casting process. After the casing 13 has been lowered intothe hole, the hole has an even cylindrical outer wall and a foundationtube can be lowered without the risk of damaging any coating on thetube.

As illustrated in FIG. 2 a foundation tube 3 is lowered into the hole 2and its upper part closed by a cap 7 through which a tube 5 is passedfor connection to a compressed air source (not shown) and a lead-in tube6 for casting mixture. In the bottom part of the foundation tube thereare provided perforations 4. For casting of the foundation tube, acasting mixture which may be, e.g. concrete, is filled through the tube6, the tube being filled with a predetermined amount, e.g. until themixture reaches a level which is indicated by 12 in FIG. 2. Compressedair is then supplied through the tube 5 above the casting mixture 11 inthe tube 13, causing it to be forced out through the holes 4 and to fillup the space between the tube 3 and the ground 1. At the same time asthe space is being filled, the casing 13 is pulled up. Alternatively,one can wait until the space is filled before pulling up the casing.When the casting mixture reaches the surface of the ground, theapplication of pressure in the space 9 is stopped and the entire space 2is thereby filled with casting mixture 8 as illustrated in FIG. 3. Thecasting mixture inside the tube is then lowered to a level 10 which isdirectly above the holes 4. In this manner the foundation tube 3 is castin position without being filled with casting mixture apart from thebottom part which covers the perforations 4. A minimum of castingmixture is thereby employed and in this manner it will be possible toadjust the rigidity of the foundation, according to the filling level.

If an insufficient amount of casting mixture has been poured into thetube at the beginning of the casting process, the compressed air willforce all the casting mixture out of the tube and compressed air will beforced out into the space 2 and "bubble up" to the surface. It will beregistered as a drop in pressure, which gives a clear indication thattoo little casting mixture has been used. In this case the only actionrequired is to supply an extra amount of casting mixture through thesupply tube 6, thus allowing the process to continue and pressure to bere-established.

In order to obtain a mast or post foundation with the longest possibleworking life, tubes are used which are coated with corrosion-resistantcoating 14, 15 both on the inside and the outside. These coatings areshown in FIG. 4. Such coatings 14, 15 can be applied by means of knownper se methods such as sintering. It is an advantage if the corrosioncoating is also insulating. A further insulating coating (not shown) canbe applied on top of the corrosion coating. This is particularlyadvantageous in the case of a mast foundation which is intended forpylons or posts which support live wires or cables. In such cases it isalso desirable to provide an earth, this being easily achieved byremoving the insulating coating at the bottom and top of the foundationtube at 16 and 17, thus enabling a contact to be established through thetube from the surface of the around to the deepest point in thefoundation. 5 In order to ensure the best possible adhesion to thecasting mixture, the surfaces of the coating are preferably rough, or anextra coating can be applied particularly in the lower part of the tubewhich Lives the tube a rough surface with a good adhesion to the castingmixture. This coating too is not illustrated in the drawing.

By means of the invention, therefore, a foundation can be provided whichcan be lowered in a minimum of time by pre-drilling a hole, the holebeing lined with the casing 13, and the foundation tube can be put intoposition very quickly and in a very simple manner with minimum risk ofdamage to the tube, or its coating.

By filling only a limited amount of the casting mixture, a saving canthereby also be made in the amount of casting mixture, which is anadvantage if the mixtures are used in inaccessible locations. Therestriction of the amount of casting mixture does not affect the qualityof the actual casting, since adequate control has been provided forensuring that the entire space between the tube and the surroundingearth has been filled. Thus the method according to the invention is areliable and rapid method of providing foundations. while at the sametime the tubes used are given a very advantageous design which providesadditional advantages, e.g. electrical insulation and an earthing rod.

In this connection it should be pointed out that problems will arise ofdestruction of the coatings if tubes with coating on the outside aredriven down according to conventional methods, where the tubesthemselves establish the hole when being driven into the ground, orwhere coated tubes are lowered into narrow pre-drilled holes.

When pre-drilling the hole in the ground, as an alternative the casingcan also be lowered into the hole with the drill head, thus immediatelyproviding a protection against the earth on the outside and keeping itin place. The drill head is therefore designed in such a manner that itcan be pulled up through the casing. There are many possiblealternatives here. The use of such casings is particularly advantageousin those cases where the soil may contain projecting stones and the likewhich can damage the coatings when the foundation tube is lowered.

Thus the invention enables tubes which are equipped with a coating to besafely lowered.

We claim:
 1. A foundation tube (3) for use as foundation for masts,posts, pillars, etc., wherein perforations or holes (4) are provided forcasting mixture (8) in the space between the tube (3) and thesurrounding material (1), characterized in that the tube (3) is coatedinternally and externally along its entire length with an electricallyinsulating, covering coating (14, 15), especially of thermoplastic, thatin addition to a covering coating (14, 15) both internally andexternally, an electrically insulating coating is applied, and thatlower part (16) of the tube (3) internally and externally is given arough surface, which provides a secure attachment to the casting mixture(8), and a roughness-forming coating is provided on the outside,especially at the lower part (16) of the tube (3), wherein theelectrically insulating coating (14) is removed in a top part and thebottom part (16) of the tube (3).
 2. A foundation tube according toclaim 1, characterized in that a stocking is shrunk on to the foundationtube (3).
 3. A method for formation of a foundation for masts, posts,pillars, etc., comprising a foundation tube (3) which is lowered into apre-drilled hole (2) in the ground, where the hole (2) has a diameterlarger than the diameter of the tube (3), wherein the foundation tubecomprises an electrically insulating coating (14) removed in a top partand a bottom part (16) of the tube (3) and where at least the spacebetween the tube (3) and the surrounding material (1) is filled with acasting mixture (8), concrete, characterized in that a casing (13) isinserted into the pre-drilled hole (2), and that a foundation tube (3)equipped with the coating (14, 15) is inserted into the casing (13),whereupon the casing (13) is pulled up, at the same time as the castingof the hole.
 4. A method according to claim 3, characterized in that thecasing (13) is inserted into the hole (2) at the same time as the hole(2) is drilled.